Predict whether the following is neutral, basic, or acidic and the pH

In summary, when considering the salt NH4Br with a concentration of 0.250 M, the fact that Br is neutral and NH4 is an acid results in an acidic solution. To calculate the pH, the equilibrium concentrations of NH4 and NH3 can be determined and used in the equation Ka = [H3O+][NH3]/[NH4] to solve for the concentration of H3O+. Then, taking the -log of the H3O+ concentration will give the pH value. The reason why the pH is not affected by the Br ion is because it does not react with water to form HBr due to its status as a strong acid.
  • #1
Jef123
29
0
1. 0.250 M of NH4Br



2. Ka for NH4 = 5.52 x 10-10 and Kb for NH3 = 1.81 x 10-5


3. So I broke the salt down into its constituents and considering Br is neutral and NH4 is an acid, NH4Br is acidic. I am just confused with how to calculate the pH. I thought that I should do this...NH4 + H2O → NH3 + H3)
At equilibrium, NH4 = (0.1 M -x) NH3 = +x and H3O = +x
Then the Ka value 5.52 x 10-10 = x2/(0.25-x) and then solve for x

The x value = the concentration of H3) and then I take the -log(H3O).

I keep getting the wrong answer, so I am just wondering if the steps I have taken are correct? Also, the pH = 4.92
 
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  • #2
I actually just the got answer. But if someone could reply in regards to why the pH of the salt solution of o,25 M NH4Br = the dissociation of NH4 to give H3O?
 
  • #3
HBr is a strong acid. As such, the Br will not react with H2O to form HBr. Thus, the pH is completely dependent on the Ka of NH4, which determines the concentration of H3O+ in solution.
 

1. What does "neutral", "basic", and "acidic" mean in terms of pH?

Neutral pH refers to a pH level of 7, which indicates a balance of equal acidic and basic properties. Basic (or alkaline) pH levels are greater than 7 and acidic pH levels are lower than 7.

2. How is pH measured?

pH is measured on a scale of 0-14 using a pH meter or test strips. The lower the pH, the more acidic the substance is, while a higher pH indicates a more basic substance.

3. What factors can affect the pH of a substance?

The pH of a substance can be affected by the concentration of hydrogen ions (H+) and hydroxide ions (OH-) present, as well as temperature, pressure, and the presence of other chemicals.

4. What are some examples of neutral, basic, and acidic substances?

Neutral substances include pure water, blood, and human tears. Basic substances include soap, baking soda, and ammonia. Acidic substances include lemon juice, vinegar, and battery acid.

5. Why is it important to know the pH of a substance?

The pH of a substance can affect its chemical properties and reactions with other substances. It is important to know the pH of a substance for various scientific and practical purposes, such as in medicine, agriculture, and manufacturing processes.

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